Grids have middleware stacks, which are a series of cooperating programs, protocols and agents designed to help users access the resources of a grid.
The most important grid middleware stacks are:
- EMI from the EU EGI project (European Grid Infrastructure)
- gLite from the EU defunct EGEE project (gLite components are now within EMI)
- Globus Toolkit developed by the Globus Alliance
- OMII from the Open Middleware Infrastruture Institute
Within LCG a hybrid set of middleware is assembled from the Globus Toolkit, the EMI/gLite middleware and older components from the EU Data Grid Project (EDG).